this is any car in Mercedes' top-of-the-line 600 series...no matter what anyone tells you, it is not a car with a V6 engine. rappers rap about driving sixes; my grandmother's Buick has a V6...which makes more sense here?

In military terms, six refers to either the commanding officer in a particular group, since the commander is usually "in the rear" or at the 6-o'clock position compared to the other members of the group. Or it can mean behind you (your 6-o'clock).